In recent years, the capacity of a circuit breaker is increased as voltage/current of a power system is increased, but a request for reducing cost and space by optimizing the structure of the circuit breaker part is increased, and it is required to secure excellent circuit-breaking performance with a lower operating force.
Gas circuit breakers including a thermal puffer type circuit breaker generally includes a puffer shaft connecting a movable-side circuit breaker part formed of a puffer cylinder, an insulating nozzle, a movable main contact and a movable arc contact to an insulating rod, and a gas passage is provided inside the puffer shaft.
The gas passage is provided for the purpose of spraying an extinguishing gas compressed in the puffer cylinder on the arc generated between the movable arc contact and a stationary arc contact, then, exhausting the gas to the movable side of the circuit breaker part.
The extinguishing gas passing through the gas passage of the puffer shaft is heated by the arc and contacts particles of a nozzle material and an electrode material melted by the arc, therefore, the gas has a high temperature and is contaminated. Due to the extinguishing gas with the high temperature (hereinafter referred to as a hot gas), the surface of the insulating rod or the inside of an insulation cylinder may be burned and carbonized, or conductive foreign substances may stick, which may drastically reduce the insulation performance and may cause a ground fault.
In Patent Literature 1, there is disclosed a gas circuit breaker including a puffer shaft coupled to an insulation rod side through a shaft guide and an exhaust cylinder provided inside a movable-side main circuit conductor so as to surround the insulation rod, in which a piston ring provided in an outer periphery of the shaft guide slides inside the exhaust cylinder. The invention contributes to the improvement in insulation performance of the gas circuit breaker by blocking a flow path through which the hot gas flows toward the insulation rod and the insulation cylinder.